The present invention relates to a method of chemical separation in a simulated(pseudo) moving bed comprising a plural number of packed beds which are filled with adsorbent for adsorbing specific components contained in a crude solution and are connected in series and circulatingly. Further, the present invention relates to a channel switching control valve which is suitable for use in the method. The method of the present invention is used, for example, for separating and extracting a specific amino acid in a high concentration from a mixture solution of amino acids.
Separation of various kinds of chemical components has been performed by means of chromatography, which utilizes the difference in the adsorption properties of the components to adsorbent such as ion exchange resin, zeolite or the like. In particular, a method of separating and extracting specific components from a mixture solution by use of a simulated moving bed which is formed by connecting a plurality of adsorbent-packed beds in series and circulatingly, is well known as an effective technique.
In the conventional method of continuously separating chemical components using such a simulated moving bed, a series of packed beds are divided into four zones as shown in FIG. 11. The continuous separation in the simulated moving bed is performed by successively shifting the functions assigned to the respective packed beds to the downstream side of liquid flow, that is, the neighboring packed beds at the downstream side by use of cutoff valves incorporated in piping for connecting the beds circulatingly and an automatic valve and/or a rotary valve for switching inflow and outflow of outside solutions, such as a crude solution, a product solution and the like.
A channel switching control valve used in the conventional four-zone-type separator as described above comprises a stationary disc (a) as shown in FIG. 9 and a rotary disc (b) as shown in FIG. 10. As shown in FIG. 11, the channel switching control valve is arranged independently of the circulating flow among the packed beds. Accordingly, a special control unit is required for the opening/closing operation of specific cutoff valves corresponding to the switching of inflow/outflow of liquid. Further, the state and quantity of the circulating flow loaded on circulating pumps widely vary corresponding to the switching operation, and load on the circulating pumps must be adjusted frequently with the change of the circulating flow. Consequently, a control system using an expensive process computer is required for detecting the timing of switching operation, the change of the amount of the circulating flow due to the switching operation, and the like to thereby adjust load on the circulating pumps.
On the other hand, a method of three-zone-type continuous separation in which packed beds are reduced in number compared with the four-zone type has been proposed (in Japanese Patent Unexamined Publication No. 91205/87). The method of three-zone-type continuous separation is suited for recovering only a specific component from a crude solution, or separating and recovering a component widely different in the ability to be adsorbed, such as recovering amino acid from an enzyme reaction solution, or the like.
When an attempt to recover a specific component is made by use of the three-zone-type continuous separator, an eluent used for eluting the specific component in the desorption zone often flows in other zones. Therefore, usable eluents are limited to specific eluents which induce no interference if the eluents enter into the adsorption zone and other zones, for example, a solvent used in the crude solution.
Therefore, there is a problem that adsorbent having the too high ability to adsorb a target component or solvent having the too high elution ability for a target component cannot be used for separating and extracting the specific component in a higher concentration.
Also in the conventional three-zone-type, a special control unit is required for the opening/closing operation of specific cutoff valves for connecting the packed beds in series corresponding to the switching operation of inlets and outlets by the conventional rotary valve, to make a continuous selective effect on the respective components in the mixture material to thereby attain a continuous separating process including adsorption/separation, desorption and recovery.